What does bug mean?
Bug is one of the most versatile everyday words in English, serving as both a noun and a verb. As a noun, it most commonly means a small insect, though in strict entomological terms it refers to insects of the order Hemiptera. In modern technology, a bug is an error or flaw in software or hardware — a usage so established that 'debugging' is a core programming activity. Informally, a bug can be a mild contagious illness ('a stomach bug') or a sudden passion ('the travel bug'). As a verb, to bug someone is to irritate them persistently. The word traces back through Middle English 'bugge,' originally meaning a frightening spectre or monster, a sense preserved in 'bugbear' and 'bugaboo' before shifting toward the creatures people feared. With roots in centuries-old English and a starring role in computing vocabulary, bug is a compact word carrying remarkable range.
An insect or small creeping creature.
"She flicked a bug off the picnic table."
A defect or fault in a program or machine.
"The update fixed a security bug that exposed user data."
To annoy or pester persistently (informal).
"Stop bugging your sister while she studies."
Informal register; common in casual speech.
Regular plural; used for insects, faults, illnesses, and obsessions alike.
"The garden was full of bugs after the rain."
The famous 'first computer bug' was an actual moth found inside a Harvard computer in 1947 — engineers taped it into their logbook with the note 'first actual case of bug being found.'
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of bug
Bug derives from Middle English 'bugge,' meaning a spectre, hobgoblin, or frightening thing, likely of Germanic origin. The same root gives us 'bugbear' and 'bugaboo,' which retain the original sense of terror. Over time, especially from the 17th century onward, the word shifted to refer to insects and other small creatures regarded with disgust or fear. Its application to mechanical and later software defects became widespread in the 20th century, popularized among early computing pioneers.
Word family
Usage notes
Highly informal in its senses of illness and obsession; standard in computing contexts where 'bug' is fully accepted technical vocabulary. In American English 'bug' often refers to insects generally; in British English it more often means a specific group of insects (true bugs) though the general informal use is widespread.
Don't confuse with
"Bug" is an insect or a software fault, while "bud" is a flower's unopened shoot or a friend.